Superchargers can be used to increase or “boost” the air pressure in the intake manifold of an internal combustion (IC) engine to increase the power output of the IC engine. The power output of the IC engine can thus be increased over the output power of the IC engine if the IC engine were normally aspirated (e.g., the piston would draw air at ambient atmospheric pressure into the cylinder during the intake stroke of the piston). Some IC engines are “horizontal” engines, with a crankshaft that normally turns about a horizontal axis. When a supercharger is used to boost a horizontal engine, rotating portions of the supercharger can rotate about an axis that is substantially parallel to the crankshaft. For example, the rotors of a Roots blower type of supercharger can rotate about a horizontal axis. Another type of IC engine is a “vertical” engine, with a crankshaft that normally turns about a vertical axis. Vertical engines have been used, for example, in power lawn mowers, and marine applications. It is to be understood that horizontal and vertical engines are not limited to operation with the crankshaft in a respective horizontal or vertical orientation. For example, a lawn mower with a vertical engine can be operated on a hill, and piston powered horizontal engines can be used in vehicles on steep grades or aircraft in aerobatic maneuvers.